This invention relates to material processing machines, and more particularly to a material processing machine for separating hard material from soft material, such as separation of muscle tissue in meat products from bone, cartilage or sinew.
Prior art deboning or separating machines typically include a compression type conveyor screw or auger extending through a separating chamber, which typically is in the form of a perforated sleeve or conduit. A combination of hard and soft material is supplied to an inlet end of the machine, such as through a hopper or a pump, and the material passes through the separating chamber under the influence of the rotating auger. The separating chamber includes a series of perforations in its walls, and soft material passes through the perforations while the hard material remains in the separating chamber and is sheared from the soft material by the action of the auger passing over the inlets of the perforations. A restriction is provided at the downstream end of the separating chamber, to create back pressure within the chamber for forcing soft material into and through the perforations. Prior art separating machines of this type are disclosed in U.S. Pat. Nos. 4,189,104 and 5,813,909, the disclosures of which are hereby incorporated by reference.
The ""909 patent discloses a separating chamber having an inner wall surface which tapers inwardly in an upstream-to-downstream direction. The perforations in the separating chamber wall are in the form of slots which are angled in the direction of rotation of the auger and which extend at a reverse angle of orientation relative to an upstream-to-downstream direction of flow of the material through the passage of the separating chamber. The auger flighting is tapered so as to correspond to the taper of the inner wall surface of the chamber, and the auger flighting edges are in close proximity to the inner wall surface of the chamber, to provide a shearing action to separate muscle tissue from bone. This type of separating machine has been found to provide a separated muscle product which is relatively coarse and has an improved texture over product obtained using a conventional separator which incorporates parallel walls. However, this type of separator must run at a relatively slow speed of operation, e.g. approximately 200 rpm, in order for proper separation of muscle tissue from hard material to occur.
A typical parallel wall separator incorporates a separating chamber with a straight-sided, non-tapered inner wall surface. The perforations in the separating chamber are in the form of round holes which extend between the inner surface and the outer surface of the separating chamber wall. Soft muscle tissue is essentially xe2x80x9cextrudedxe2x80x9d through the perforations under the influence of pressure within the chamber, and the auger functions to shear off the hard material and to convey the hard material toward a discharge end of the separator. This type of separation provides an end product that has a generally pasty composition which is not suitable for uses which require coarse or textured ground meat. Accordingly, the end product is sold at a price significantly less than that which can be obtained for a coarser grade of ground meat. In this type of separator, the same quality of end product is obtained regardless of the speed of rotation of the auger. Accordingly, the auger is rotated at a relatively fast rate of speed, e.g. approximately 1500 rpm, so as to provide a high output of soft material.
As can thus be appreciated, prior art separating machines are capable of providing either a high output of relatively low grade soft material or a low output of a higher grade of soft material. Known separating machines are not capable of providing a high output of a higher grade of soft material.
It is an object of the present invention to provide a separating machine having a relatively high throughput and which is able to produce a soft tissue product having a coarser texture than can be obtained using prior art high throughput separating machines. It is a further object of the invention to provide such a separating machine which involves a modification to the perforations in the separating chamber, and which otherwise utilizes components which are common to prior art separating machines. It is a further object of the invention to provide a separating chamber for a separating machine, having a unique slot configuration which enables production of a relatively coarse meat product, and which is capable of use in a high throughput application with similar components as are employed in prior art separating machines. Yet another object of the invention is to provide an improvement in a high throughput separating machine, which improves the quality of separated soft material which can be obtained using the machine.
In accordance with the invention, a material processing machine for separating relatively soft material from relatively hard material includes a separating chamber having wall structure which defines a flow passage extending between an upstream end and a downstream end, and a fluted auger located within the separating chamber. The auger rotates in a direction of auger rotation for advancing material from the upstream end of the separating chamber toward the downstream end. The material processing machine further includes a pressurization arrangement which maintains pressure on the material as the material passes through the separating chamber. A series of perforations are formed in the wall structure of the separating chamber. Soft material passes through the perforations as the material is advanced through the separating chamber by the auger. The perforations extend outwardly through the wall structure of the separating chamber, and have a unique configuration which defines a low pressure flow path between the flow passage of the separating chamber and the exterior of the separating chamber. Soft material from within the flow passage travels through the low pressure flow path to the exterior of the separating chamber.
Each perforation is configured so as to have an inlet at the inner surface of the wall structure and an outlet at the outer surface of the wall structure. Each perforation includes an outwardly divergent wall arrangement, such that the inlet has a lesser area than the outlet to provide a restriction at the inlet to the perforation. This construction provides an increasing area for the perforation in an inward-to-outward direction, which serves to define the low pressure flow path for the soft material, to enable the soft material to travel from the flow passage of the separating chamber through the perforations and to the exterior of the separating chamber.
The perforations are preferably in the form of slots which extend generally in the direction of material flow within the flow passage of the separating chamber. The slots are preferably oriented in the direction of rotation of the auger, in an upstream-to-downstream direction. In all other respects, the slots are oriented in a reverse direction relative to the material flow and the direction of auger rotation, to alleviate pressure within the slot and to provide the low pressure flow path for material passing from the internal flow path of the separating chamber to the exterior of the separating chamber.
The invention also contemplates a separating chamber with a slotted perforation configuration as well as an improvement in a separating chamber, substantially in accordance with the foregoing summary.